1. Field of the Invention
The present invention relates to an on-vehicle video camera which is mounted on a vehicle such as an automobile and which is suitable for providing visibility of an area to the left or right side of the vehicle.
2. Description of the Related Art
Typically, vehicles such as automobiles include an inside mirror, called a rearview mirror, and outside mirrors, called sideview mirrors, in position, to easily provide increased visibility of the driver's blind-spot areas to the rear, left, and right sides, etc., of the vehicle.
In some kinds of vehicles, however, structurally, the above-noted mirrors may sometime be insufficient to provide visibility of such areas. In order to overcome this inconvenience, various kinds of so-called back monitor systems have been put into practice in which a rear-vision video camera is attached to the rear end of a vehicle so that an image captured by the video camera may be displayed on a monitor at a position visible to a driver.
The on-vehicle video cameras for use in typical back monitor systems often use relatively compact photographic video cameras which are available for normal photography without being changed or with a slight modification. If such a commercially available standard video camera is used, an image can be captured in sufficient light, resulting in a successful image obtained from the output of the video camera when driving outside during the daytime. During night travel, however, a video camera is likely to capture an image in light as low as the video camera can, and the image displayed on a monitor would possibly make the captured object unidentifiable.
Since taillights of an automobile include a backup light which is turned on in response to the vehicle moving in reverse, the backup light may be used for a light source for illuminating the imaging area of a video camera for use in a back monitor system. Thus, night photography can be achieved at a certain level of illuminance.
Another recent proposal is that a video camera for use in applications other than a back monitor system is mounted on an automobile to provide visibility for a driver. However, there is no light source for a video camera for use in applications other than a back monitor system which is turned on in response to the operation of the automobile, leading to a problem in that a video camera which is mounted on the vehicle in order to photograph a particular area may not be used during night travel. For instance, a driver usually uses an outside mirror, called a sideview mirror, to view an area to the left or right side of the automobile; however, only use of outside mirrors may not provide sufficient visibility of the driver's blind spot areas. Thus, there has been proposed a video camera mounted at a predetermined position on the left or right side of an automobile to provide increased visibility. However, it is difficult for such a video camera mounted at a position on the left or right side to successfully photograph during night travel unless a special camera for night vision is used.